The present invention relates to a method and apparatus for the flexible assembly of a plurality of automotive body styles on a single assembly line with zero loss of production during changeover.
Current body assembly lines typically use a palletized approach for assembling components of the automotive body style to be built and for joining those components to one another at a framing station. The palletized approach requires that sufficient pallets be provided for each type of body style to be assembled and transported along the assembly line at one time, including spares for any pallets that may be damaged during the assembly process. When this number is multiplied by the number of models to be produced on the assembly line, the number of pallets can be a very large number requiring large amounts of off line storage space and also requiring a tremendous amount of maintenance to maintain the accurate geometry required of a palletized fixture.
It would be desirable to reduce the number of pallets required for a modern automotive assembly line capable of producing a plurality of automotive body styles on the same line without any loss of production during changeover. It would be desirable in the present invention to provide an assembly line configuration capable of building a single automotive body style, two automotive body styles, three automotive body styles, or four automotive body styles without loss of production, and without requiring excessive changes in the production line configuration. It would be desirable in the present invention to provide an overhead component delivery system for the early stages of the assembly line, while providing a palletized transportation system between the workstation beginning at the underbody respot station. It would be desirable to provide an overhead transport system for the component assembly line which is capable of quick and efficient changeover of body style fixtures to produce different body styles without interruption of production. It would be desirable to provide a flexible assembly workstation having an interchangeable workpiece support or geometry fixture for the different body styles to be manufactured through the workstation, where the different support fixtures can be interchanged with one another without loss of production.
A flexible automotive body assembly line according to the present invention includes an overhead component transport system. The overhead transport system preferably is provided for the bodyside left hand assembly line, bodyside right hand assembly line, and underbody assembly line and tack workstation. After the underbody is tacked at the underbody tack workstation, the underbody is transported by an overhead transport system and transferred to a palletized system at the underbody respot workstation. After respot, the pallet system transfers the underbody to the framing workstation, where the bodyside left and right hand components are delivered by the overhead system.
The framing workstation positions the left hand and right hand components of the bodysides to the underbody and tacks the right and left components with respect to the underbody. The pallet then transfers the assembled workpiece to the roof framing fixture and continues through the framing respot workstation where additional welding and tacking is performed. The pallet system then transfers the assembled framed body to closure workstations where closure panels can be assembled prior to delivering the assembled body to the paint station.
Preferably, the overhead delivery system for the bodyside left hand assembly line, the bodyside right hand assembly line, and the underbody tack workstation is an electric monorail system. The electric monorail system can provide an overhead rail extending between the various workstations, and preferably extends in a circular or loop configuration passing through the workstations and through a workpiece support or antler exchange workstation for preparing the overhead delivery system to receive and transport different body styles or models through the assembly line without any loss of production. The electric monorail system can include a carriage powered by an electric motor for movement between the workstations along the overhead monorail. Downwardly extending supports or pillars extend from the carriage for receiving the workpiece support or antlers there between. The workpiece supports or antlers are interchangeable as required for engaging the particular body style or model of components to be manufactured through the assembly line. The vertically extending supports or pillars include a telescoping function to allow the workpiece support or antlers to be moved from a vertically raised position used to transport the workpiece or components between workstations, and a vertically lowered position at a workstation to deliver the workpiece or a component to the workpiece support, nest or geometry fixture at the particular workstation. The vertically extending supports or pillars also include latching mechanisms to hold the workpiece support or antlers in the raised position during transport between workstations. Preferably, the drive for unlatching and lowering the workpiece support or antlers and supported workpiece or component is provided at each workstation, and includes a single drive for each vertically extending support or pillar of the electric monorail carriage system. Preferably, the single drive for each vertically extending support or pillar of the carriage located at the workstation is capable of unlatching the latch mechanism prior to lowering the workpiece support or antlers at the workstation location, and after the work has been performed at that workstation raising the work support or antler portion of the carriage to the raised position and latching the latch mechanism of the vertically extending support or pillars from the carriage prior to the carriage leaving the workstation.
The present invention also includes a flexible body assembly workstation. For purposes of illustration, a single workstation will be described. The flexible body assembly workstation can be used at the bodyside left hand assembly location, the bodyside right hand assembly location, the underbody tack assembly workstation, or any other major subassembly component. The workstation preferably includes an overhead component delivery system extending through the workstation. The overhead delivery system can enter the workstation empty, or can deliver a partially completed component to the workstation for additional assembly steps. In either case, a workpiece support or geometry fixture is provided at the flexible body assembly workstation for receiving the parts to be built up into the component to be transported, or to be added to the partially completed component delivered by the overhead system. The workpiece support or geometry fixture at each flexible body assembly workstation is interchangeable to match the body style or model to be manufactured at the workstation for that particular operation cycle. Preferably, the flexible assembly workstation includes sufficient capacity to handle up to four different workpiece support or geometry fixtures for use on demand at the workstation depending on the particular body style or model to be manufactured at the workstation. In one configuration, the workpiece supports or geometry fixtures are connected to a delivery system capable of moving the fixtures between the standby or storage positions and a ready position for receiving the workpiece component to be delivered to the workstation. In the alternative, a workpiece support or geometry fixture can be delivered using an xe2x80x9cH-Gatexe2x80x9d configuration. The H-Gate delivery system uses a linear transfer system, such as a rail delivery to the workstation ready position and between two standby or storage positions on either side of the station. The standby positions are serviced by two transversely extending delivery systems. One delivery system is provided on each side of the workstation producing the xe2x80x9cHxe2x80x9d configuration for which the system is named. The transversely extending delivery systems provide, or pre-load, the next workstation support or geometry fixture required at the workstation. For changeover, the current workpiece support or geometry fixture and the new workpiece support or geometry fixture are reciprocated simultaneously along the rail system bringing the new workstation support or geometry fixture into the workstation and removing the previously used workpiece support or geometry fixture from the workstation. When properly located, the rail transfer system stops in the appropriate position for the geometry fixture to be positioned at the workstation. The old workpiece support or geometry fixture is then removed from the standby position by one of the transversely extending delivery systems. The process is then repeated by pre-positioning the next desired geometry fixture at one of the standby positions for subsequent delivery to the workstation on demand.